Brake squeal occurs upon application of a vehicle brake when the structure of the brake drum resonates at its natural frequencies due to forces imparted by the brake pad frictionally engaging the inner surface of the brake drum. The sound pressure level produced by the vibrating drum can become objectionable to receivers in the immediate area thereby prompting manufacturers of brake drums and driveline systems to modify the brake drums using various means. The resulting reduced amplitudes of vibration reduce the sound level produced when brake squeal occurs.
Prior art methods of reducing the vibrational amplitude of a brake drum have included adding various additional structures such as retention bands and/or damping layers to the outside of the drum with varying degrees of effectiveness. The problem with these prior art approaches generally has been the complexity and expense introduced where the cost benefit ratio has not proved to be practical. Another significant problem introduced whenever a layer of material is added to the outside structure of the brake drum is that the rate of heat rejection is dramatically reduced, thereby reducing the service life of the drum. Examples of these prior art methods can be found by reference to U.S. Pat. Nos. 2,349,658 and 2,639,195, the disclosures of which are hereby incorporated by reference.